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What is involved in changing runway/taxiway/approach lighting?
When a runway inspection determines that there are bulbs out on any of the runway or taxiway lighting fixtures, what is involved in changing them?

Does the runway/taxiway need to be shut down for all bulb changes? (Obviously for center line markers, but what about edge markers?)
What is involved in changing bulbs for any sort of landing system lighting? (i.e. ALS, PAPI, VASI, etc)

To answer your two questions:

Unless the runway is a very busy one, or the failure is such that it can have an adverse effect on the safety of operations, runways are not closed to replace failed lamps.
Bulbs are not changed in the field, with rare exceptions such as PAPIs. Typically, the maintenance team will have hot spares ready to be installed of every kind of fitting. In the event of a failure, they will replace the whole fitting, which can be done in a few minutes, and replace the bulb at the workshop.

The replacement of a fitting typically involves the isolating of the circuits, untorqueing and disconnection of failed fitting from circuit, connection of new or serviced fitting, torqueing, and powering circuit again.
In the case of PAPIs, the bulbs are replaced on site. The replacement is done by opening the PAPI box, and replacing the halogen bulb.
By the way, bulb changing is becoming obsolete with the wide adoption of LED airfield lighting.

Interesting. Do you have any references to support that statement? Changing the whole fixture out seems like much more work than just replacing a bulb.

On the contrary, changing the bulb would require you to remove the fitting anyway, plus the extra steps to open the fitting, replace the bulb, close back the fitting again... it actually takes more time. Furthermore, it is much more difficult to ensure the watertightness of the fitting. Replacing the whole fitting makes the complete process predictable and fail proof. You don't want to delay operations more than you need to because of a bulb...

LED lighting needs to be replaced too at times, just far less frequently.

Sure, but what I meant is that LED fittings do not have bulbs.

Runways are not closed for bulb changes. Closing a runway is a big hairy deal that is not something you do unless you have to.
Normally what happens if it is a multi-runway airport is that they wait until the runway is not being used because of cross wind conditions, then a guy in a yellow truck with flashing lights drives out and makes the replacement.
If there is only one runway, or if something has to be done to an active runway (like remove a turtle or something), then the FBO operator or tower just warns off any approaching aircraft on the CTAF while the dude in the yellow truck scoots out there and does it.
Normally they try to stay off the runway with the actual truck and minimize the time they are out there. So, for example, with a turtle what happens is the guy drives the truck on the grass until he is parallel with the turtle, then he leaves the truck's lights on, runs out, grabs the turtle, and runs off the runway again. He then drives the truck back (on the grass) and the FBO resumes operations.

Is a turtle a FOD risk?

@curious_cat I don't know, but sometimes they can get pretty big and you definitely don't want to run over one.

Runways are not closed for bulb changes Ummm, actually sometimes they are. For example they don't generally change the threshold lighting lamps while aircraft are taking off or landing, and if you only have one runway you can bet your jetblast-blown behind the runway is closed until the crew is done changing the bulbs. It may only be closed for a few minutes, but it is most definitely closed and not available for takeoff or landing operations.

@voretaq7 I think you are using a different definition of "closed" than I am. A "closed" runway by FAA regulations has a VERY specific meaning which involves NOTAMS, runway markings and other stuff. You cannot legally close a runway for "few minutes". Just because the tower is waving off pilots, does not make a runway "closed" in the FAA sense.

@TylerDurden While a NOTAM should theoretically be filed for all runway closures (even brief ones) I can tell you for a fact it's not done in practice: Brookhaven (KHWV) routinely closes their crosswind runway for banner tow pick-up/drop-off (they roll out the lighted Xs and everything) without filing a NOTAM for it: they'd need to file one for each wind shift! A work crew at the threshold of a runway & instructions (radio or visual) not to land there meets the definition of a "temporary closure", but if you want to argue that interpretation with airport management or the FAA you can.

@TylerDurden Also with respect to the process for closing a runway via NOTAM, it's not at all complex. My example for Brookhaven could be handled with a few keystrokes (simply submit two NOTAMs stating RWY 13 CLSD and RWY 31 CLSD and cancel them when whatever condition requiring the closure is cleared). The (US) NOTAM system has been substantially upgraded since most of us started flying: with direct digital NOTAM submission for authorized persons (like airport managers/ops people) it's pretty dynamic and responsive these days.

@voretaq7 It's not that simple; the NOTAM has to be issued something like 30 days ahead of time and the runway has to be marked with 3 X's on both ends, at a minimum. You can't close a runway with a radio because some aircraft do not have radios, OR the radio may be malfunctioning OR the pilot may have it tuned to the wrong frequency OR he may miss the announcement even if he is on the right frequency.

@TylerDurden That's only partially correct: Temporary closures can be issued with immediate effect (Think about it: Entire AIRPORTS are sometimes temporarily closed with immediate effect due to accidents.) This is getting far afield of the topic of this question though, if you'd like to continue this discussion stop by chat and I'll be happy to continue talking about it.


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Where is the camera in the A320?
On the A320 family there are circuit breaker panels in the cabin between the exits. On the 2000VU panel there is a "camera" circuit breaker (C5 position):

Top: Source -- Bottom: A320 CCOM p165 -- Right: A320 CCOM p166
Which camera is it related to?

I believe, but have no evidence, that it's an option for one that looks out the front windshield, dashcam style. It was apparently a thing in the 1980s. Cockpit next to it is for United Channel 9.

There's an option for a tail mounted camera for the passenger entertainment system (PES). It's the same one they use on widebody jets, but it's not hooked up to the cockpit for taxi purposes.
Airbus press release says

Designed for a private customer, this cabin seats just over 30 passengers and includes such features as touch-screen technology, advanced passenger entertainment and communications, plus a tail-mounted camera.

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Is it possible to sail a seaplane?
Say a seaplane has ditched onto ocean or a very large lake due to engine failure. Is it possible to sail the plane to the shore using wind alone, similar to sailing a boat?

Based on Terry's answer, it seems to be a very different process from sailing a sailboat. To sail like a sailboat, you'd have to deal with the surface area of the plane that the wind hits, and also erect a sail of surface area large enough to overcome the effects of the plane's surface area. There also has to be something that does the job that a keel does, and you need a rudder that acts in the water (not an airplane rudder). Finally, you have to have control over the angle of both the rudder and the sail. Those are the minimum elements for a vessel to be a sailed like a sailboat.

@ToddWilcox: Apparently seaplanes do have water rudders, and long narrow floats should provide some lateral drift resistance even without a keel. (That's how catamarans work.) You don't have anything like a proper sail, of course, but the body of the plane should still catch some wind, and the rudder will provide some limited aerodynamic control. So I can believe that something vaguely similar to sailing a sailboat might be possible, at least on some limited range of headings and wind speeds.

You can sail a seaplane, but there are a lot of considerations. For starters, it makes a big difference as to whether you're talking about a seaplane where the hull is in the water or a floatplane. A floatplane sitting up on its pontoons (floats) is more up in the wind, but it's also more susceptible to rough water because of its higher center of gravity.
My personal experience with sailing a floatplane was with a J-3 cub with an 85 horse engine on rivers and lakes. If we wanted to back onto the shore, we had to sail it since there was no reverse pitch propeller.
For purposes of explanation on how to do it, let's say that there's no wind, but we're on a river with enough current that the movement of the floatplane with the current when the engine is off gives the floatplane a wind relative to the water. Further let's say the river is flowing from east to west, and we want to back onto a beach on the north shore. We land and stop the engine upstream from the beach. As the floatplane drifts it will weathervane into the wind. Thus, with the controls neutralized, we'll be facing west and moving downstream in mid-river with the current, but not as fast the current because of the drag of the wind on the aircraft.
The rule of thumb is that you point the tail towards the shore you wish to get to. We do that by applying left rudder and right aileron. Thus we have increased the drag on the left wing, which will swing the nose left, and the left rudder will also swing the nose left. Thus the nose is now pointed a few degrees toward the left shore (south), the tail toward the right shore (north). The airplane will then sail to the right shore (north) relative to the direction the aircraft nose is pointing because the the aircraft is moving backwards relative to the water.
The trick in this instance is vary the control input to arrive at the downstream point you want. For practice, I used to have students sail to alternate sides of the river on Oregon's Willamette River downstream from the city of Eugene.

I never had this particular experience, but I once ran out of gas in a boat in the middle of a lake and used my swim fin as an oar to get me to shore.

After trying and failing to visualize your example, I assume there must be a typo somewhere in your answer, specifically between "we'll be facing west" and "the left shore relative to the aircraft, in other words the north shore." Those two statements surely can't both be correct; if the aircraft is facing west (and is, hopefully, not upside down :), the left shore should be the south shore. Having no personal experience of floatplane handling characteristics, however, I can't tell which part of your answer might need fixing.

I find the rule of thumb that you "point the tail towards the shore you wish to get to" rather counter intuitive. Can you explain why it is that that works (assuming it's not part of the typo)?

@Blckknght, I believe that you point the tail toward the destination shore because you want to back the plane in. If you point the nose toward the shore, you'll have to back out, and that's more difficult in a plane without a reverse pitch prop (it probably involves someone getting wet).

@Blckknght: Actually, if I'm visualizing this correctly, it makes sense. You have effective wind coming from ahead (i.e. from downstream), and any aerodynamic lift effects are probably fairly negligible, so the plane mostly interacts with the wind via drag, which pushes it back (= upstream). Since the plane is at an angle to the stream, however, the wind drag force will have both a lateral component (which the floats, like catamaran hulls, will partly resist) and a longitudinal one (pointing towards the tail of the plane, and thus pushing the plane towards the bank the tail is pointing to).

@Blckknght: ... Basically, the key realization, in sailing terms, is that you're not tacking the plane into the wind (without a proper sail, it can't really do that), but rather sailing it with the wind, backwards! That would be a ridiculous way to sail a sailboat (the sails won't catch the wind properly, and the rudder would be unstable), but for a plane with ailerons to provide drag, and with an air rudder to maintain stable heading, it apparently works.

@Blckknght That's because As the floatplane drifts it will weathervane into the wind.

@Terry There does seem to be something wrong in your answer. It says you're facing west. Is the plane travelling forward or backward?

@IlmariKaronen You are correct, good catch, and I have revised my answer. Another senior moment on my part (they seem to be occurring more often). The plane is traveling forward with respect to the river bank, but backward with respect to the water. The nose is pointed west (downstream) and a little south when the control input is applied; the tail is pointed east (upstream) and a little north with the control input.

@Blckknght A good number of the students I instructed for their float plane rating also found that rule counter-intuitive initially. The thing to remember is that you're moving backwards with respect to the water and thus toward the shore the tail is pointing to.

"Non-Flight of the Navigator"?

It's been done at least once before.
In 1925 a US Navy PN-9 landed in the Pacific when it ran out of fuel on the way to Hawai'i. The crew then rigged a sail from parts of the canvas wings and sailed their plane over 400 miles (in nine days) to reach the islands.
http://timeandnavigation.si.edu/multimedia-asset/naval-aircraft-factory-pn-9-116-scale

"Non-Flight of the Navigator"?

I know this is not what was asked, but I couldn't resist. There was indeed a seaplane that could be sailed: A sailplane with a seaplane hull. It was a curiosity and built only because none had been built before - or ever since.

DFS Seeadler floating on water (picture source). First flight was in 1935, and the official reasoning was to create a modern sailplane for clubs without access to a good airfield, but a lake nearby. But I guess the designer Hans Jacobs knew already how flimsy the official reasoning was: Below the keeled fuselage bottom was a wooden skid to allow landing on land.

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Does the centre of pressure of a cambered airfoil go ahead of the quarter chord point when angle of attack is increased?
I got two figures and answers which are seemingly contrary. In wikipedia, it says the the location of the centre of pressure of a cambered airfoil is just behind the quarter chord point at maximum lift or high angle of attack. But in other websites, I see the centre of pressure well ahead of the quarter chord point. Which of the below two pictures is correct?

The lower one is better. Details depend on the camber.
A flat plate or a symmetric airfoil have their center of pressure at the quarter chord point. Angle of attack changes change the lift produced, but the center of pressure stays at the quarter point (as long as the flow does not separate). This is exactly true for two-dimensional flow; as soon as we look at real wings with limited span, the exact location of the center of pressure moves forward at the same angle of attack with lower aspect ratio. The center of pressure of a slender body is approaching the leading edge. But your question is about airfoils, so the rest of this answer looks at 2D flow again.
Positive camber contributes lift independent of angle of attack, and its center of pressure location depends on the shape of the camber. A camber line shaped like a segment of a circle has its center of pressure at 50% of chord, and the camber line of rear-loaded airfoils is even farther back.
The resulting location of the center of pressure is the sum of both, camber and angle of attack effects. At low angle of attack the camber line dominates this location, so it is somewhere at mid chord. At high angle of attack the center of pressure shifts forward towards the 25% point. Note that this behavior will make the isolated airfoil unstable in pitch.
A negative camber will reduce lift and result in a center of pressure location ahead of the 25% point. Increasing the angle of attack will now shift the center of pressure back, again towards the 25% point. Now you have a stable pitch behavior (when the airfoil pitches up, the center of pressure moves back and creates a correcting moment change), such that a conventional airplane which loses its horizontal tail can still fly on when inverted. The center of gravity will determine the trim speed, and control may still be possible either by moving the wing flaps or by shifting the center of gravity. Theoretically, at least. I have witnessed an experienced model aircraft pilot doing this after the horizontal tail of his plane was lost in flutter, but the resulting glide speed did not lend itself to a smooth landing.

So is the first figure is wrong? Its a positively cambered wing and the centre of pressure is way close to the leading edge.

@GokulJ: Yes, I guess it is exaggerated on purpose to drive the point home, which leads to a wrong location.

@GokulJ: The upper picture becomes correct if we look at a real wing with a rather low aspect ratio. For an airfoil in two-dimensional flow the last airfoil in the first picture is wrong; for a stubby wing it could be right.

Sir, what do you mean by "resulting location of centre of pressure is the sum of both" ? And I cannot understand how, if the second figure is correct, a horizontal stabilizer will make the aircraft trimmed. The lift gives a pitch down moment about the CG which is increased if there is a horizontal stabilizer. how do you make the aircraft trimmed at AOA 9 degrees in the second figure?

And why does the first picture become correct for a low aspect ratio wing, Sir ?

@GokulJ: Trim: The horizontal can produce either lift or downforce. In all cases of the second picture a downforce is needed for trimming the aircraft. For the other question please read the expanded answer or post a new question.

Sir, how do I read the expanded answer

@GokulJ : as we look at real wings with limited span, the exact location of the center of pressure moves forward at the same angle of attack with lower aspect ratio. Meaning the first picture becomes correct for a cross section through a stubby wing like on the Space Shuttle, but is wrong for a wing of a regular airplane.

Sir could you explain why that happens ?

@GokulJ: Not in the comments. Ask a new question already.

Yes Sir. I will ask a new question.One last thing.  By "resulting location of centre of pressure is the sum of both" did you mean that the resulting location of centre of pressure is the combination of the theoretical location(considering 2D flow) and the effect of the finite wing span ?

@GokulJ: No, it is a superposition of the flat plate and the camber effects. Potential flow is linear, so its effects can be added.

I think it will move forward.
If you look at the picture below, you'll see that the pressure increases at all top surface locations with increasing angle of attack. But the suction peak at the front does this in a much faster fashion.
As a consequence the centre of pressure moves forward.
I can image that this might not be true for all airfoils, but this is the development that I saw most of the times.

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Is there any instrument similar to a compass but which I can electrically drive?
I would like to build a home weather station with analog instruments showing for example temperature, wind speed and wind direction.
I would like to use a salvaged flight instrument to show the wind direction: I have a wind vane transducer that convert the wind direction in an electrical signal and I would like to use this signal to drive a suitable instrument.
The instrument I have in mind is like a magnetic compass but while the magnetic compass does not need an "input signal" I need to drive the needle.
I have a look at a heading indicator

but it seems to me that the "airplane needle" is fixed while the 0-360 graduation is moving. I need, like in a compass, a fixed graduation and a moving needle.
For example this seems fine to me but I have no idea what instrument is:
MASCO SERV. CORP.
DALLAS, TEXAS
PART NO. 503A
SER NO. 2500

The title asks one thing, but the body seems to ask another. Do you want to identify what instrument is that? Do you want to know if there is some model of electrical compass? Something else?

@Federico I am interested in answers to the title question. The instrument I posted is just an example. What is an electrical compass?

Does your transducer output digital or analog angle values? If this is the later, you likely need some amplification to adapt the transducer output voltage and power to the input range of the instrument used for display, and correct the linearity. Solutions exist in the actuator world and your best friend is a small stepper motor with an analog-digital converter (if the sensor output is digital and the phase coding is compatible, you will only need the digital portion).

@mins My transducer output analog 4-20mA signal.

Your best bet is to try and use an ADF readout, also known as a Fixed Card ADF (its most likely what you have pictured in your question). There are a few variants of the display out there and it will require some hacking to make it do what you need but it should suffice. As these units are generally considered "older" technology you may be able to get a read out for fairly cheap. On the even older side you can look for a Radio Compass/Radio Direction Finder which is quite similar.
Note: A heading indicator is NOT what you want. While you could pull one apart and install some kind of drive system to make it do what you want it is not, as it stands what you want.

The issue with these is that they use a synchro or resolver type interface.  You'll need a matching synchro or resolver generator at the sensor to make them work together.  Aside from availability, standards for synchros are 'flexible' which means that unless you have a matched pair, getting them to work together is a major headache.

Full Flight Simulators have compasses that are driven by electrical signals, not earth magnetic fields. There are quite a few older type sims such as B737-200 being scrapped, you could get a good deal there.


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How long can an F-16 stay supersonic?
I've been wondering for awhile to myself, how long can one stay supersonic?
How long before one ran out of fuel?
What would the issues of staying supersonic be (aside from control)?

Depends on how much fuel that they have on board.   You're not gonna be able to hold wing tanks or a centerline tank on that jet and still be able to fly supersonic, so we will have to assume that we can only use internal fuel. In a Block 50/52  F-16C, the jet holds about 7200 pounds of internal fuel with the tanks topped off. In full afterburner, the jet's F100 or F110 engine is burning approximately 800 pounds of fuel per minute.   This gives a maximum of approx. nine minutes of flight time in full afterburner.  So you  have at most nine minutes of supersonic dash available to you.
As mentioned above, while an F-16 is capable of a maximum speed of Mach 2, it can't do this unless it's in a clean configuration, that is, it does not have any external stores on the jet which create a lot of parasite drag and prevents supersonic flight with ordnance on board. Typical mission speeds are high subsonic (500-600 KTAS) for cruise and combat maneuvering.  Usually afterburning is utilized for brief periods in order to quickly accelerate the jet, such as to shorten takeoff distances, or to quickly replenish energy which has been bled off during maneuvering.  Supersonic dash can be used to egress a FLOT or airspace deep inside enemy territory once, say a bombing mission is complete and you have been informed by an E-3 that there are enemy fighters scrambling towards your position.  You jettison the external stores, save maybe a pair of AIM-9s or AIM-120s on the wingtip rails, push open the throttle and run like hell - and hope it's enough that you can make it to a friendly airbase or a tanker in time!

OK for the nine minutes in full afterburner, but does the f-16 need full afterburner to stay supersonic? I'm not sure it can perform supercruise (I may be mistaken), but after going supersonic, (i) it may take time to go back in subsonic after shutting down the afterburner and (ii) it may stay supersonic with less than full afterburner.

@ManuH i.e., how long can the F-16 "coast" while supersonic? Hit the burners, get to M1.3 (for example), shut down to flight idle, how long before the needle drops below M1...

While the time seems not unreasonable, are you sure this fuel burn is at the altitude and not static? There will be dramatic difference between the two. And, as @Mahu mentioned, it is likely that F-16 is speed limited not by power but by other constraints (in most of its envelope).

You can absolutely go supersonic in an F-16 while carrying wing tanks and ordnance.

If you can, it's pretty limited - say Mach 1.05 or so.  I'd need the performance charts on the jet with the drag indexes, specific ordnance loadout, etc.  But external stores create a tremendous amount of parasite drag on the airplane.

Fuel is one limitation, structural limits are another one. Fighters with good all-around view usually feature rounded canopy designs. This may lead to a stagnation point to be located on the canopy structure. Stagnation points are characterized by zero flow velocity, the kinetic energy of the flow is converted into inner energy of the fluid. As result, the fluid temperature is drastically increased. Canopy material and Mach number determine the period this temperature load can be sustained.
As reference, check aircraft designs like SR-71, Mig-25, or Concorde whose mission is characterized by permanent supersonic operation. These designs often feature flat, angled cockpit windows to avoid stagnation points.

Don't worry about the materials. The simple pitot intake is what limits the F-16 to about Mach 1.6 - go faster and intake efficiency tanks. With full AB you barely make it to Mach 2, for a short while.

"Don't worry about the materials." Did you take that from the de Havilland handbook for Comet engineers?
Seriously

"Don't worry about the materials." Did you take that from the de Havilland handbook for Comet engineers? Seriously, just because maximum performance is limited by one fact does not mean that performance endurance is limited by another fact. The limitation of the canopy temperature is caused by cumulated thermal loads, thus depends on the period of exposure.

According to a post by SCPanda on this site, the F-16 can attain supersonic speed without afterburner:

You can, and I have done it several times after I finished my missions and was flying back home.
Conditions:
Full throttle without the burner
Clean loadout but with LAU-129s of course.
Fuel normally below 5000 lbs (which is a lot in the viper, it can stay in the air for a long time with 5k lbs if you know how to manage your fuel).
Altitude was around 20k to 25k.
Then fly straight and level and watch the mach value, it will go above 1 mach.

If that F-16 was a version with an F100-PW-220 engine, the specific fuel burn at full military power would be 0.73 lb/(lbf * h). So with 5,000 lbs in the tanks and maximum thrust of 14,590 pounds-force without afterburner, the plane would burn through the fuel in 5,000*60 /(0.73 * 14,590) = 28 minutes
Minus some time to reach M=1 and some fuel for landing...about 20 minutes (?)


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Why is the rear seat ejected before the front one?
On aircraft with 2 crew placed one in front of each other (tandem) equipped with ejection seats, the rear seat is ejected before the front one (described here for the F-14).

Why is the rear seat ejected before the front one?
Is an aircraft without ejection seat (e.g. glider) evacuated in the same order and why?

Have you not seen Top Gun? It's so the front seat can hold the rear seat afloat till the rescue chopper arrives!

There is no sequence in a glider. Everyone tries to get out as best as he can, but there are very few cases. The few I have heard of involved an instructor in the back seat, and in one case the instructor pulled the student out before jumping himself. When facing forward it is simpler for the rear seater to pull out the forward seater than vice versa.

If the front seat ejected first, the drag would probably bring him too close in the trajectory of the rear seat, thus making a collision of both probable.
Since the rear seat is ejected first, it experiences drag earlier than the front seat and will thus not have an increased probability of hitting it.

Also flames from ejection rockets could possibly burn the second seat.

Geeze, it isn't drag it is the plane's velocity, unless the plane is going backwards. So look at the sequence (1) front seat goes first, (2)then the plane goes forward, (3)then the second seat ejects. In such a sequence the second seat is ejecting "under" the first seat, thus the two could collide. Also If front seat goes first then the fume/fire from front seat ejection are swept over the second seat.

@MaxW actually, an ejection seat configured to fire "straight up" will inherit the forward velocity of the plane, so the front seat will go up-and-forward, with a forward component exactly corresponding to the velocity of the plane.  Thus, the front seat would be "right over head" when the second seat is fired.  However, when you add wind resistence into the mix, the ejection seat will begin to drift backwards relative to the plane (which is far more aerodynamic).

I suppose you could tilt the ejection seat backwards a little to cancel out the forward velocity and fire straight up in a ground frame, but that'd be very speed specific, so it seems like an unlikely engineering solution.

@CortAmmon: I'm pretty sure you want all of your ejection-seat rocket's delta-V separating the pilot from the plane, so they don't get clipped by the vertical fin (or some other part of the plane if it's travelling at a crazy attitude in a spin).  The acceleration is already high enough to be very stressful on the human body, so you can't just use bigger rockets.  There's just no good reason not to let wind resistance do the work for you, once you get the pilot clear of the plane.

@MaxW: Read about "conservation of momentum". Without drag from air, the seats would continue travelling forwards at the plane's velocity. Unless the plane is actually accelerating, "then the plane goes forward" is nonsense.

@LightnessRacesinOrbit - except that air drag is present; quite a bit of it. The aircraft is much heavier and more aerodynamic than the pilot and ejection seat, and at ejection the aircraft's often still under power, so the force of drag slows the ejecting pilot relative to the aircraft, so the aircraft would move forward relative to the pilot (or the pilot would move rearward compared to the aircraft, either way).

As far as trajectory of ejection, most fighters have what's called a "zero-zero" ejection seat; the seat is capable, using booster rockets, of getting the pilot high enough and far enough away from the aircraft that it can be used at zero altitude, zero forward airspeed and/or groundspeed. This allows it to be used during emergencies on the ground, such as a fuel leak and fire or an armed weapon detonating on the rail (both of which have happened). A zero-zero seat, used as such, actually launches the pilot forward because the rockets are placed toward the rear of the seat.

Here's a simple video showing the difference between older explosive seats and newer zero-zero seats: https://www.youtube.com/watch?v=Z1cnvJO1TF8 At speed, the forward trajectory is still present, primarily to ensure the pilot gets enough distance from the aircraft to clear the tail before drag slows him.

@KeithS: Yes, that's exactly my point. It's drag. Max was suggesting that drag had nothing to do with it, that somehow once the pilot had ejected the plane magically continued on without her.

In general, in aircraft with tandem seating, the rear seat (having the Radar Officer) ejects first, followed by the forward (pilot) seat, after a delay of ~0.3 seconds. This is done for a few reasons:

If the pilot seat is ejected first (or both are ejected simultaneously), there is a possibility that the pilot seat may collide (as it will be dragged backwards due to wind force) with the copilot seat or damage the (rear) canopy during ejection.
In some aircraft, the pilot can eject only after the rear seat is ejected. This is so that, in case the rear seat fails to eject, the pilot can still control the aircraft and 'pop out' the Radar officer's seat by maneuvering. For example, the F-4 procedure called for the pilot to roll the aircraft inverted with a positive 'g' and then pop the radar officer with a negative 'g'.

In some cases like the (Mig-15 UTI), the rear seats were ejected first simply because the gas jets from the pilot seat ejection mechanism made ejecting from the rear compartment impossible.

and I'd not like to get a rocket blast from the front seat in my face if I were in the rear seat...

@jwenting if you must evacuate the aircraft, wounds are only the second most important thing (the first one being stay alive).

@ManuH having your face burned off by a rocket blast isn't conducive to staying alive...

Neither is smashing head first into another ejection seat's bottom.

I'd think the main reason would be to avoid cooking the rear seat crew while the rockets were firing as well as to avoid an accidental collision between the front seat and the rear seat crew. After all - the jet is likely to be travelling forward at a relatively high velocity when the two are coming out of the plane (or what's left of it).

The pilot ejects last so that he/she can attempt to remain in control of the aircraft.

Do you have some source or reference for this? I'm not saying you're wrong, but it's always good to provide as many details as possible.

I'm pretty sure that if the pilot wanted to remain in control of the aircraft, he wouldn't eject at all, and, conversely, he would only eject if he had already lost control of the aircraft, or he knew that such loss of control is imminent and certain.

This is supported by the story in this answer to a related question.

Again no sources, but more anecdotes. He might eject the rear seat in attempt to minimize risk to human life while he does a difficult landing (I vaguely remember something with parachutists that jumped out of a malfunction plane, while the pilot landed safely later). Also possible: To keep the plane under control for a few more seconds before he eject, instead of screwing over the rear seat.

@Dorus - Every aircraft ejection system I know of triggers every ejection seat in the aircraft when one handle is pulled; you can't selectively eject your copilot/GIB and stay in the plane. In larger aircraft like the B-1B and B-52, not all crewmen are in an ejection seat, so the flight crew may delay ejection as long as possible until those crewmen can bail out another way, but when he pulls the handle, barring a malfunction, everyone in a rocket seat is gone.

As far as the pilot ejecting last to stay in control, the time difference between the rear seat and front seat ejection is less than a second. A lot can happen, but if the decision has been made to eject, "control" is not under consideration.

If the pilot pulls his handle it will always initiate a command eject sequence.  Non-pilot crew members may eject themselves without anyone else being ejected, and in some aircraft a non-pilot crewmember may also be able to select a command eject sequence.  However, there is no way for a pilot or anyone else to selectively eject someone else while they remain in the aircraft.

ADDENDUM:  The above is based on my personal experience in the 4 seat EA-6B, but I would challenge anyone to find an exception to my statements.

The F-14 had an EJECT CMD selector on the pilot’s Landing Gear Panel, below EMERG STORES jettison and the NOSE STRUT switch. In the usual MCO mode, either crew member could command ejection of both, RIO first. In PILOT mode, the pilot still ejects both and goes second;?the RIO only ejects himself.


text:
Are there items bigger than an aircraft section transported by air today?
This question about engine transportation made me wonder what is the size of the biggest item ever transported. Then I remembered that it should have been a space shuttle (either Buran or the American Space Shuttle), but those items are no longer transported. Nowadays whole aircraft sections are transported, thanks to A300-600ST and B747LCF.
Are there cargo items bigger than a high by-pass ratio jet engine or an aircraft section that are transported by air today (in 2015)? How are those item handled?

Today no, in the recent past it was the space shuttle. An entire aircraft

Is SpaceShipTwo considered "cargo" akin to the shuttle?

does the size of the cargo count? A small aircraft can be larger than a large aircraft section... Or an M-1 battle tank, or a patrol boat, both of which have been transported by C-17s.

When you are not restricted by the size of a cargo hold, your cargo can become much bigger. See below how a Mil-26 lifts the fuselage and wing root of a Tu-134. I have not checked whether this is a record, but I would expect that the world record will involve the Mil-26 somehow.

Mil-26 lifting a Tu-134 carcass, seen from below (source)

I almost forgot an helicopter can carry cargo thanks to sling!

Hmmm... So, I guess it depends on how you define 'aircraft section' as to whether this counts as "bigger than an aircraft section" or whether it counts as being an aircraft section. :) It's at least bigger than a fuselage section.

@reirab Chinooks and Super Stallions (and others) lifted entire jet fighters, including F-4 Phantoms, not small aircraft by any means, in Vietnam. They could do it today, and maybe do on occasion (maybe in Afghanistan).

@jwenting: … but if you need to airlift an MH-47E from 8500 ft, the Mi-26 is your only bet!

According to Wikipedia, the An-225 is the world's largest cargo aircraft and it's transported both the heaviest and longest items of cargo ever carried by air:

On 11 August 2009, the heaviest single cargo item ever sent via air
  freight was loaded onto the Antonov 225. At 16.23 metres (53.2 ft)
  long and 4.27 metres (14.0 ft) wide, its consignment, a generator for
  a gas power plant in Armenia along with its loading frame, weighed in
  at a record 189 tonnes (417,000 lb)
[...]
On 11 June 2010, the An-225 carried the world's longest piece of air
  cargo, when it flew two new 42-meter test wind turbine blades from
  Tianjin, China

It's also carried the Buran spacecraft (the 'Soviet space shuttle'), which was actually what the aircraft was originally built for.
The An-225 is still in operation and the operator gives some examples of large cargo that can be carried:

The aircraft has the spacious cargo compartment with length of 43.32
  m, width of 6.4 m and height of 4.4 m, that allows carrying a variety
  of cargoes inside. For instance,

sixteen standard aeronautical containers of UAC−10 type;
50 cars;
single piece of cargoes up to 200 t (turbines, generators, dump trucks − Belaz, Kamatsu, Euclid, etc.).

I'm not sure if this counts since it's still in development and production, but Scaled Composites' Stratolaunch Carrier Aircraft (dubbed the Roc) will almost certainly shatter any existing records for payload capacity. Its mating system is designed to hold up to 500,000 lb (230,000 kg.) Its intended payload, like that of WhiteKnight and WhiteKnight 2, is a rocket stack mounted between the twin fuselages to be air launched. At least as of December 2011, the first flight test was indeed scheduled for 2015, so I guess it technically does meet the 'in 2015' criterion for this question. :)
The specific 'item to be carried' in this case is the Pegasus II rocket stack with a gross weight of 465,000 lb. (211,000 kg,) according to Aviation Week.
Stratolaunch carrier aircraft carrying a Pegasus II:

Source: BusinessInsider
The carrier aircraft will also have the largest wingspan of any aircraft to date:

Source: Wikipedia

On first glance I thought that 3D model was made up in Kerbal Space Program :)

@AlexanderJohansen what do you think SC uses in lue of Autocad ;)


text:
What are the pros/cons of all-moving rudder?
All-moving flight control surface (stabilator instead of a stabilisator+elevator) are common on supersonic aircrafts but this is usually used for pitch control only. For rudder, this design (one all-moving piece instead of 2 separated pieces, the rear one being the one moving) is not common. The only example I think of is the SR-71. What are the reason for adopting this all-moving rudder on the SR-71? Why is it not spread? In short, what are the pros and cons of all moving control surface for yaw control?

The PAK FA/T-50 has all-moving stabilators, and so does China's J-20.

Related: last paragraph (before footnote) here: https://aviation.stackexchange.com/a/97244/34686

All-moving control surfaces are like regular surfaces, only that the moveable part extends over 100% of the chord. Since the effectivity of a control surface grows with the square root of the chord fraction $\lambda$ of its moveable part, an all-moving (also called full-flying) control surface has twice the effectivity (defined as normal force change per degree of movement) of one with a 25% chord length of its moveable part.

Effectivity of a control surface over chord fraction $\lambda$
Hermann Glauert was the first to calculate the inviscid lift due to control deflection, and the result of his work is shown above. The truth (as defined by wind tunnel results) is somewhere between his curve and that of my simple approximation.
Control surface in subsonic flow
Deflecting a flap causes the camber of the control surface to change. This is a positive effect in subsonic flow and allows the resulting airfoil to create more lift in the desired direction. Also, the orientation of the leading edge is maintained, causing much smaller suction peaks there than when the full surface is deflected. Suction peaks require a long pressure rise, which promotes flow separation when its gradient is too steep.
Control surface in supersonic flow
In supersonic flow, camber increases wave drag, so the full-flying control surface is more effective. Pure supersonic flow has no suction peaks, and flow separation is less of a concern. Therefore, full-flying surfaces are better for supersonic flight, while hinged surfaces are the better choice in subsonic flow. Especially in transsonic flow, at least a moveable stabilizer is necessary to avoid control reversal due to the contour break of a hinged control surface.
Stealth aircraft
Stealth aircraft benefit from large, coherent surfaces, and the gap of a control hinge will increase their RCS. Even subsonic stealth aircraft like the Lockheed F-117 and the Northrop Tacit Blue use full-flying control surfaces for their ruddervators, as does the supersonic Northrop YF-23.
Why the SR-71 rudders are special
An intake unstart at Mach 3.2 is a violent event, and the SR-71 needed all the yaw control authority available to compensate for the sudden asymmetric loss of thrust. Its rudders were optimized for supersonic use, and the actuator could be driven to its extreme position by an explosive charge which was fired automatically when an intake unstart was detected. To ensure optimum intake operation, the engines were positioned at mid-span, and the yawing moment of thrust changes was much higher than that of conventional fighter aircraft which have their engines close to the centerline for better roll agility. In addition, they use their rudders mostly in subsonic flight; only the size of the vertical tail is determined by yaw stability at top speed.

Your paragraph about the SR-71 made me quite curious. Do you have any reference to read more about this aircraft's flight control system?

@ManuH: Those details are from Ben Rich's biography. I guess most if not all of it can now be found on SR-71 fansites.

Pros:

Higher rudder sensitivity; moving the entire vertical stabilizer increases the surface area redirecting airflow, allowing higher yaw rates using rudder only.
Better performance at low airspeeds, for much the same reason.

Cons:

Increased forces on the vertical stabilizer at higher speeds, possibly in excess of materials strength; requires a limiter system such as FBW to account for airspeed and reduce stabilizer rotation at higher speed to produce a constant yaw force for a given rudder pedal input and to prevent overstress.
Increased interference drag. Interference drag occurs when aerodynamic surfaces meet at perpendicular angles; air being moved in one direction encounters air being moved perpendicularly at the same time, causing energy to be spent compressing the air. All-moving control surfaces typically preclude the use of fairings to reduce this phenomenon.
Causes more of a roll moment in the direction opposite the yaw. Stabilators on fighters are also often used as "elevons", producing roll as well as pitch control. A vertical all-moving surface in the same configuration as an ordinary tail would provide an unbalanced force on the top of the airframe to roll the aircraft in the opposite direction to the yaw, only magnified by the increased surface area redirecting airflow. You could correct this with an equal or at least offsetting vertical all-moving surface below the empennage.
Interference with horizontal stabilators. Traditional elevators/rudder are easier to keep out of each others' way, but when the entire stabilizer rotates, this becomes more difficult. Typically pitch is emphasized over yaw, and so an all-moving vertical stabilizer would be limited in total travel even at low speed to prevent binding the horizontal stabilator. You could stagger horizontal and vertical surfaces but that reduces the moment arm that the closer one has, offsetting the gains of an all-moving surface.

Other reasons it's not used when stabilators are include the fact that emphasis in aerobatic airframe design is typically on maximizing pitch and roll. Rudder is typically used to augment yaw produced by bank in a coordinated turn and so the amount of force the rudder provides is of least overall importance compared to the other primary control surfaces.

You can control rudder forces easily by picking the right hinge line. There is no need for FBW when control forces need to be tailored.

Having flown an aircraft with an all-moving stabilator and no anti-servo tab, a more sensitive  all-moving rudder is definitively not a pro, but a con. The rudder is a blunt force instrument to keep the airplane coordinated, and doesn't require the fine grained control of the elevator or aileron to maintain precise altitude and heading.


text:
Can anybody confirm which aircraft is in this picture?

Image Source
Does anyone know what airplane is shown in this picture? It looks like the Republic F-84, but I'm not sure because the front landing gear is under the nose on the F-84 and this one is further back.

Based on what I find from the marking on the plane of "8-MV", it appears to be a Dassault Mystère IV A. The image on the non-Wikipedia page looks identical to the one in your image (I can't put that image here because it is copy-protected).

Image Source

Try this image: https://commons.wikimedia.org/wiki/File:Dassault_Mystere_IV_(4229072236).jpg

I concur. Intake, canopy, rivet lines, and gun port all match.

Thank you so much...I could not have figured it out without your help!

Even the font of the 8-MS / 8-MV match, and the exact positioning of the 'lightning flash'


text:
Which is the technically correct term: Nose Gear or Nose Landing Gear?
Talking about landing gear system, came across my mind the correct and technical name. Is it NOSE GEAR or NOSE LANDING GEAR?

I find the term "Landing gear" rather misleading, is it retracted for taxi and take-off?

The terms are interchangeable.  I've seen Boeing maintenance manuals refer to it as a 'Nose Gear'.  But both terms are fine; people will understand it either way.

Based on the ATA iSpec 2200, ATA Standard Numbering System, which provides a standard for structuring maintenance data by the manufacturers. The structure helps the airlines by providing a common structure regardless of manufacturer.  While voluntary, most aircraft manufacturers use it.
The spec is organized into chapters by aircraft system. ATA Chapter 32 is LANDING GEAR. Chapter subsections cover subsystems.  Subsection -10 is Main Gear and Doors and subsection -20 is Nose Gear and Doors.  So that's the 'common' terminology in the aircraft manufacturing and maintenance world.

From FAA order 5300.7, Nose Gear seems to be the correct word.


text:
Where to download a specific flight route before the flight?
Is it possible to download the flight route before the flight?
I'm interested in a table (or something similar) containing the following data:
Timestamp | Coordinates | Human readable location
————————-—+————————————-+—————————————————————————
                       ...

This would be quite helpful, so I can follow the airplane progress during the flight, without having internet connection.
Where can I get that from?

You won't be able to get the actual flight plan since they are not public - why would they be?  You can get a similar possible flight plan from any number of online flight simulation planning sites, for example this one.  However, there are many possible routes between two airports and even the same flight by the same operator will differ from day to day.

@Simon, I don't know what to think about this short article. Is there a possibility to ask for this information supposed to be public (before the flight, if I understand correctly)?

Well, Repetitive flight plans are actually public in Brazil: http://www.cgna.gov.br/?page_id=148

From what I know, you can "decode" certain routes on flightaware.com which will bring up this which may be the closest thing possible to what you want.

Yeah but this is "after the fact", not before the flight like the OP is asking. Best bet is to look up the last flight that day between the destination and see that route, it should be close at least.

@RonBeyer You can find these for flights even before they are planned to like this.

@SMSvonderTann That is not necessarily the plan. It's just one that's used before.  Actual flight plans are not made public - there is no need for them to be.  Flightaware and other such flights use "after the fact" and guesswork.

@Simon I don't know if it's guesswork but on Flightaware they don't show up until shortly before the flight and the ones I've tracked usually follow them.

No, such information is not publically available.
It does exist, of course, but in order to obtain it, you would have to know a dispatcher or something similar, and they would have to be willing to disregard their confidentiality agreement.
You could always find the specific flight (flown on a previous date) in a website such as FlightAware of FlightRadar24, and see which route it flew. The route will likely be similar, but not necessarily the same.


text:
How are VORs oriented near the magnetic poles?
I noticed on SkyVector that, for example, the Resolute Bay VOR (YRB) and Baker Lake VOR (YBK) seem to be oriented in such a way that the 360 radial is pointing in the direction of true north (and I don't think the variation is anywhere near zero there).
I know VORs are supposed to be oriented according to magnetic north, but is it common practice close to the magnetic poles to have them point true instead? If so, is there any way to tell if a particular VOR is doing just that, except looking at the chart and noticing that the small arrow is pointing north rather than off to one side?

In Canadian Airspace, Northern Domestic Airspace (NDA) is the area of compass unreliability within which runways and NAVAIDs are oriented to true or grid north versus magnetic north.
You should not need to worry about which NAVAID is to true north; simply keep track of whether you're in Southern or Northern Domestic Airspace.

Cool, how do I know which airspace I'm in, is it visible on the sectionals or something?

The Canadian LO charts shows a black line with T letters along the border. It's also clearly labelled as Northern Domestic Airspace (Compass indications may be erratic. True tracks apply). Here's an example of  how it appears on the LO 5 chart. Canadian LO5 Chart

VOR stations in areas of magnetic compass unreliability are oriented with respect to True North.
I don't think you can tell if it's pointing true north by looking at the charts. However, it doesn't really matter anyway because your own compass would be unreliable as well when flying in the vicinity of such a VOR. After all, when navigating using a VOR, you don't fly a heading, you fly a radial.

Sure you fly a radial and not a compass heading, but which one? Unless you only want to fly to the station and never leave, you might want to intercept an outbound one, makes it pretty important which way they're pointing, or you might end up discovering santa's workshop. :) And you can tell from the small arrow on the chart which way radial 360 is pointing, so it's not impossible, but that little arrow is pretty subtle, especially if you're in the air trying to figure out which radial to use when your GPS breaks down.

Incidentally his is also true of runway numbering: In parts of Canada you'll find runways numbered with true (rather than magnetic) headings because the magnetic declination is so extreme using magnetic headings is impractical.

If you're flying anywhere near those weird VORs, you're either IFR or you've plotted your intended route on a chart in relation to the VOR. If your compass is unreliable you'll have to rely on GPS or VOR radials anyway.

Let's say you're relying on GPS, it breaks down, and you look at your chart and your plotted course, decide you want to use the outbound radial of a VOR to bring in the right direction, now should you use the magnetic or true course from your navigation log, usual answer is magnetic, which would put you maybe 20 degrees off course, which at 40 miles from the station is a 14 miles deviation. Of course you're right, but let's say I didn't note the radials and only the course; or for that matter, it's easy to miss during planning, you can't say it doesn't matter which way is north.

Let me answer that with a question: if you were flying in that area, would you be using magnetic courses and headings in your navigation log?

Both, I always do, everywhere. And you're probably right, it's not easy to accidentally have a VOR along your route be oriented differently from the rest. The closest I could find was Frobay to Hall beach, which is over 400 miles, the rest are all NDBs, pretty much. Still, I guess I'd like it to be more obvious that they're not magnetic somehow... and you still need to know if it points true or magnetic north, or you will dial in the wrong radial :)

If you're flying in an area where a magnetic compass is known to be unreliable, you would NEVER use magnetic headings for navigation. It just wouldn't make sense.

You're missing my point, you still need to know if the VOR is oriented according to true or magnetic north, or you will pick the wrong radial, regardless of how you fly. As I mentioned, Frobay uses magnetic. There will always be a border between VORs being magnetic or true, and you need to know that you're about to cross that border. This is regardless whether your compass is reliable or not, it's all about the VORs and turning your intended route into the correct radial.

In areas of large magnetic declination, approaches and runways are given in true instead of magnetic headings, designated by T after the heading, such as RNAV 13T approach. If you are assigned a VOR radial, just follow that radial whether it is true or magnetic.
The important thing is that you don't use magnetic headings on a true approach. Look out for that capital T up north.

Cool, didn't know about the T. If you're not being assigned a radial, but selecting one yourself, do you know if there's a way to determine if the VOR is using true north or not, except for the tiny arrow on the chart?

It doesn't look any different on the chart. You should be able to check the Facility Directory (or Canadian counterpart) for the magnetic variation. Here's some info for using one in an approach:  http://www.avcanada.ca/forums2/viewtopic.php?f=54&t=78868

Even in areas where compasses are not actively unreliable, magnetic variation changes over time so that VORs and runways might no longer be aligned to their nominal magnetic bearings.  Runways are usually renumbered to correct this, but old VORs are usually left in place because many charts depend on their original alignment.
As well as magnetic and true north systems, there is a "Greenwich" system used for polar navigation which is aligned to the prime meridian rather than to any local concept of "north".  I'm fairly sure this is used by aircraft that overfly either pole, but there are no permanent navaids or runways that would be aligned to such a system.


text:
Can you go around with LAHSO in effect?
Some larger airports in the US use land-and-hold-short (LAHSO) operations, meaning you're cleared to land, but only if you're able to do so without going beyond specific point (usually an intersecting runway) on the roll-out.
What if you're forced to go around just before touch-down, perhaps even with the mains hitting the pavement, you will inevitably head straight for, and cross, that intersecting runway. Would there be a risk of colliding with aircraft operating on the intersecting runway?

The AIM contains guidance on LAHSO operations and specifically says (in bold; I didn't add the emphasis in this case) that the clearance does not stop you from going around, but if one becomes necessary, the pilot should avoid other aircraft and vehicles and notify ATC as soon as possible:

AIM 4-3-11 Pilot Responsibilities When Conducting Land and Hold Short Operations (LAHSO)
5. If, for any reason, such as difficulty in discerning the location of a LAHSO intersection, wind conditions, aircraft condition, etc.,
  the pilot elects to request to land on the full length of the runway,
  to land on another runway, or to decline LAHSO, a pilot is expected to
  promptly inform air traffic, ideally even before the clearance is
  issued. A LAHSO clearance, once accepted, must be adhered to, just
  as any other ATC clearance, unless an amended clearance is obtained or
  an emergency occurs. A LAHSO clearance does not preclude a rejected
  landing.
6. A pilot who accepts a LAHSO clearance should land and exit the runway at the first convenient taxiway (unless directed otherwise)
  before reaching the hold short point. Otherwise, the pilot must stop
  and hold at the hold short point. If a rejected landing becomes
  necessary after accepting a LAHSO clearance, the pilot should maintain
  safe separation from other aircraft or vehicles, and should promptly
  notify the controller.

And because I hear some pilots get the readback wrong, the next paragraph covers the proper way to read back a LAHSO clearance:

7. Controllers need a full read back of all LAHSO clearances. Pilots should read back their LAHSO clearance and include the words, “HOLD
  SHORT OF (RUNWAY/TAXIWAY/OR POINT)” in their acknowledgment of all
  LAHSO clearances. In order to reduce frequency congestion, pilots are
  encouraged to read back the LAHSO clearance without prompting. Don't
  make the controller have to ask for a read back!

If there is any doubt, don't accept the clearance in the first place.  If something happens after you have accepted it and you aren't positive that you will be able to hold short, go around as early as possible to maintain as much separation from whatever may be crossing your runway.
There is a lot more guidance in that section of the AIM which I would highly recommend that any pilot flying in to a large airport reads.

There's always a risk with LAHSO and pilots can always say "unable"; student pilots are not even permitted to accept a LAHSO clearance. You can always go around if you deem it necessary; you're the pilot in control and empowered to make all decisions affecting the safety of your flight, and the fact that you're landing on a LAHSO clearance is just a factor you need to take into account. Making the decision to go around is, in my estimation, much safer than landing and potentially crossing the hold short line (due to the reaction time others have to deal with the situation).
While there is that risk, the tower is watching and at any sign of trouble they will call other landing aircraft off. The two runways aren't being landed on at the same moment such that normal operations would cause them to collide at the intersection if one didn't hold short.
According to this interesting article on the subject, there were 20 LAHSO incidents between 1994 and 1999.


text:
How is V_S0 calculated for anything less than maximum weight?
Is there a way to (safely) calculate the stall speed of an aircraft ($V_{S0}$) for anything below maximum weight? All the tables in the POH are valid for maximum weight only, and stall speed can drop significantly with a light load. As a consequence, if you're flying the published (max weight) $V_{ref}$ on final, you'll actually be carrying a significant amount of extra speed and thus increase the required landing distance, possibly in quite a dramatic fashion.

All aerodynamic forces are proportional to the dynamic pressure, which is the product of air density $\rho$ and half of the square of flight speed $\frac{1}{2}v^2$. If your flight mass is reduced, reduce the dynamic pressure proportionally to keep all other parameters the same. To express this in terms of speed, you need to multiply the posted speed in the handbook with the square root of the mass ratio, like that: $$v_{reduced\,mass} = v_{full\,mass}\cdot\sqrt{\frac{reduced\,mass}{original\,mass}}$$

While I'm pretty sure this is mathematically correct, could you elaborate how dynamic pressure relates to mass? Am I correct when I think you're saying that since the gravitational force is reduced, we need to reduce the amount of lift accordingly, and lift depends linearly on dynamic pressure?

@falstro: This is exactly right, I use the fact that lift force equals weight (mass times acceleration g) at a load factor of 1 (horizontal, unaccelerated flight). So I scale the dynamic pressure proportional to mass. Lift is dynamic pressure times area times lift coefficient, thus the dynamic pressure varies linearly with mass at a load factor of 1, when the others (area and lift coefficient) are kept constant.

Ok, great. And the lift coefficient depends on the AoA, right? Thus if we adjust the dynamic pressure (and maintain a load factor of 1) as the weight is reduced to keep the lift coefficient constant, we'll have a constant AoA. That makes sense. Thanks! By the way, load factor of 1 is unaccelerated flight, not necessarily horizontal, approaches are usually descending :)

@falstro: Yes, you are correct, but the cosine of 3° (assuming this is your approach angle) is so close to 1 that I did not want to make the answer more complicated. The main thing is that the aerodynamics stay identical between the different mass cases (sloppy again: This is neglecting changes in Reynolds Number ;-)

The small GA aircraft approach is usually 1000 feet in about a mile, so it's closer to 10 degrees on average but I suppose it's usually flattened out closer to the threshold, could this have a substantial effect on the maths? After the flare, it's practically horizontal so that's ok, but you don't want to end up in an accelerated stall in the flare. Also, Reynolds numbers. That triggers some deeply buried dark memories.  ;)

If the aerodynamics are the same, you can make the comparison at any load factor. Just be careful and compare same with same (only change mass and adjust speed with the given formula so all other parameters stay constant).

Please correct me if I'm wrong but for a C172 taking off at gross weight and full fuel (approx. 2300 lbs) and landing with 1 hr of fuel reserve remaining from its original 42 gallons of fuel (approx. 2100 lbs), the reduction in stall speed is only about 4.5%.  Not enough to make any changes to approach numbers.  The percentage of weight lost due to fuel burned would have to be much higher before this effect would become relevant.


text:
What would happen if the entire blade on a turbojet engine went supersonic?
I have seen that when a blade tip goes supersonic, there are vibrations and lower efficiency. If the entirety of the blade was to go supersonic, would it be more efficient?

Not much if designed for it, but efficiency will suffer. Also, if the blade is not designed for the loads, the all-supersonic flow could overload it.
How would you achieve the desired all-supersonic flow? By cooling the intake temperature or increasing the rotation speed, of course. Cooling is less practical, so lets assume you run the compressor faster. This would mean higher centrifugal loads, and the increased dynamic pressure would drive up aerodynamic blade loads with the square of the speed increase.
Also note that compressor blades for subsonic flow are highly cambered. Supersonic blades would better be uncambered. Thus, the blade would only function well if both its aerodynamics and its strength are designed for the full supersonic speed. A regular blade would perform poorly and probably fail. However, even an optimized blade would show lower efficiency due to the inherently higher aerodynamic losses in supersonic flow.


text:
Why was the experimental MiG 1.44 so similar to the experimental TKF-90?
Why was the MiG 1.44 so similar to the MBB TKF-90? (for some information on the TKF-90 you have to scroll down this question, it is the only one source I knew about this particular plane)
Here is the MiG 1.44:

(source)
Here is the TKF-90

(source)
For me, these two aircraft are nearly unrecognizable. They were adversaries in those times, not partners. Has that similarity arised only because of the similar expectations from these airplanes?

It wouldn't be the first instance of the USSR stealing another aviation design. In fact, most of the USSR Buran Space Craft was "stolen" via public repositories published by NASA during the Shuttle development (and fed false data as well).

If it was public, than it was not stolen, isnt it? Or at least the USSR can claim that they had good spies.

Notice the quotes around "stolen"? Basically yes, it was public domain, but stolen in the essence that they didn't come up with it themselves and took it through a spy agency, the KGB/VPK. The linked article also notes that the KGB spied on resources related to the TU-144 project, which looks remarkably similar to the Concorde...

I once led a group of Antonov engineers through the aircraft exhibition of the Deutsches Museum in Unterschleissheim near Munich. There are two halls connected by a walkway, and from that walkway you can see the restoration workshop which is located between those halls.
When the group had long left the walkway, one engineer still stood in the middle of it and gazed down at the Dornier Do-31 which at that time stood in the shop for cleaning and repairs after many years in the open. I walked back (with one of our interpreters) and asked him what fascinated him. He said to me that this was the first time he saw this aircraft in person. And he continued that he knows every rivet in it. He had studied it in the early Seventies for several years when Antonov was tasked with developing a VTOL transport aircraft. In the end, they abandoned the idea (like NATO did a few years earlier), but this airplane had been the center of a part of his life.
Don't think bad of this - it is just good engineering practice to study what others have done. If you want to develop something, look what others have done before you and try not to repeat their mistakes. You might as well marvel at the similarities between an F-15 and a Su-27, a Concorde and a Tu-144, or a Space Shuttle and a Buran. In the end, they were designs made for the same purpose, and it is no wonder that they turned out alike. It just means the engineers did their job properly.
In nature this is called convergent evolution.

I would agree with "convergent evolution" had the two designs started off separately and then ended up the same, but at least in the case of the Buran and the TU-144, they actually diverged from a single design, not converged...

I agree. I was just curious.

@RonBeyer: The Russians had studied deltas before French or British engineers did. Looking at the Concorde drawings did not reveal anything new to them. Agreed, the Buran was a me too, but only because the military was scared to be left behind. If you look at the actual capabilities, the Buran was quite a bit better. Could the Shuttle fly as much off range? Could it land autonomously?


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Which fixed-wing aircraft has the highest number of required flight crew members?
Most modern airliners require two pilots to operate. Older airliners require a flight crew of three: two pilots plus one flight engineer.
Has there ever been an aircraft where the number of required flight crew members is extraordinarily high, for example five or six?
To clarify the question:

"required flight crew member" is the number required by relevant regulations, not the number needed to physically operate the plane. If that number is not met, the plane could not legally have taken off
gunners / weapon operators of military aircraft who are not necessary for a safe flight are not included
flight attendants are not included

Possible duplicate of Which airplanes require two (or more) pilot/operators?

@RoboKaren: Not really a duplicate.

More of a related as the linked question is for contemporary airliners.

Do you mean flight crew members? Flight attendants are required crew members for many large aircraft operations, and the required number of flight attendants can easily be 5+ in addition to flight crew.

@JonathanWalters flight attendants are only required if passengers are onboard (-:

Yes, by relevant regulations flight attendants are required crewmembers in order to takeoff legally when passengers are aboard. Certain operations also legally require additional flight crewmembers when passengers are aboard, or when a certain number of passengers are aboard. The distinction between required flight and non-flight crewmembers is relevant.

@JonathanWalters The number of required FAs could actually be even 10 or more, depending on the size of aircraft and seating arrangement. The general rule is 1 FA per 50 pax. IIRC, there are some A380 configs flying with 500+ seats.

@reirab Exactly! And for the FAA it's generally per 50 pax seats, occupied or not.

I can't find a good source, but I believe the Kazakh I'll-76 in the Chakri Dadri mid-air collision had a 5-member flight crew. I believe it was 2 pilots, flight eng., navigator and radio operator.

This question makes me wonder what the minimum required crew for Airforce One is.

@Mast: hey, I have an idea - why not take the plane up with Trump onboard, then have the crew bail out one-by-one until the plane can't fly anymore! Anything for science..!!!!

@Mast -- it's four: two pilots, a F/E, and a nav (at least for a functional check flight) -- doubt it's changed since the 90s

It's only sort of fixed-wing, but the Mil V-12 had a crew of 6: pilot, co-pilot, flight engineer, electrical engineer, navigator, and radio operator.

In addition to the An-225, a few historic examples at five, a couple at six, and one (possibly) at seven.
I don't know how firmly worded regulations were at the time so I can't speak as to whether all of them were absolutely required to be in place for takeoff. As neither of the six-crew airliners entered service, the question might be moot for them anyway.
Two prototype airliners with six -

The Bristol Brabazon had a crew of six - two pilots, navigator, radio operator, two flight engineers.
The Saunders-Roe Princess also had six; again, two pilots, two flight engineers, radio operator and navigator. (I can't find a clear statement, but see this cockpit diagram)

At least one operational airliner had a minimum of five -

The Boeing 314 had a flight crew of five - two pilots, a navigator, a radio operator, and a mechanic. However, for the intended long-duration flights, it apparently carried two full crews plus two additional people - a chief engineer and a clerk. Relief crew are probably outside the scope of your question, but it's not clear to me if the two additional crew would have been "required" even for a shorter flight (the engineer maybe, the clerk probably not) - so the answer might be six.

And some military aircraft with five or more -

The Zeppelin-Staaken R.VI apparently had a flight crew of seven (commander, pilot, copilot, radio operator, fuel engineer, and two engine mechanics) - I say apparently because that list doesn't seem to mention gunners. There may have been some duplication of roles.
The Linke-Hofmann R.I (did not enter service) appears to have had a flight crew of six, but the details are sketchy.
I think the basic "flying" crew of the B-36 was five, after taking out everyone with a combat duty - two pilots, one engineers, radio operator & navigator; see this list - but it's hard to break out the exact roles and determine who was there for relief purposes. The XC-99 cargo variant also had a crew of five, which seems consistent with this.
The Me 323 transport had a crew of five not counting gunners (two pilots, two flight engineers, radio operator)

The British "V" bombers had crews of five.  Two pilots, an air electronics officer, navigation RADAR officer (doubled up as refueller on the Victor and later on  the Vulcan) and navigation plotter.  There were two additional stations for relief pilots and crew chiefs and long range "ranger" flights.  I believe that the B52 crew is similarly made up.

Five was very common for long-distance aircraft: pilot, co-pilot, engineer/mechanic, radio operator, and navigator.

@Simon I think the Vulcan bomber carried 5 officiers on the flight deck, but there was only two ejector seats for the pilots. If the other 3 had to bail out of the plane, well the procedure was awful and you would either die sitting in the plane when it crashed, or die hitting the plane when you jumped out of it.

"two pilots, one engineers, radio operator & navigator" on the B-36 adds up to four, not five. Did you mean two engineers?

@DanHulme: Two pilots. One engineer. One radio operator. One navigator. Compare e.g. Saunders-Roe Princess.

Oh, "radio operator & navigator" isn't one position. This is why we need the Oxford comma! :-)

@mickburkejnr - well, that could lead to some awkward conversations. "Well, lads, it looks like we're going down. Now, as there's only two ejector seats for the pilots, I'm afraid you lot will have to stay in the aircraft, or use the ridiculously dangerous and very likely fatal manual bail-out procedure. Now, who's for the 'stay in the plane without a pilot' option and who's for the 'probably fatal procedure'? Come on, now, don't just sit there sitting on your hands with murderous looks in your eyes and...oh. Oh, dear. Now, let's not do anything hasty here, lads, nothing unfortunate..." :-)

@BobJarvis Fortunately for the pilots, they could bail out of that conversation pretty easily...

A clerk?! To do the flight data recording, I suppose:)

@BobJarvis in the documentaries I've seen about the Vulcan, that was basically the conversation. Everyone on the plane knew the score if the plane was shot down. Luckily I don't think they lost any crew on the Vulcan, as I think one was destroyed but didn't contain any crew.

@Pavel it seems the "flight clerk" had the duties of a ship's purser - responsible for paperwork, some cargo (eg mail), and generally dealing with passengers; this presumably explains why the term "purser" is now used for the senior steward. This article from 1938 gives an idea of the role - and, interestingly, clearly differentiates them from the "steward".

@Pavel thinking about it, this would probably make a good question in its own right :-)

The Antonov An-225 Mriya requires a crew of six- you have the pilot, copilot, 2 flight engineers, navigator and a communications specialist/radio operator.

An-225 cockpit; image from sas1946.com

Seems like some older An-124 also require six crew.

The smiley-face upholstery is...disturbing...and is that red book a Bible? (Let us read from the Book of Aircraft, chapter 12, verses 7 through 22: And then St. Orville spake, saying: "Oh, Lord, bless this, thy AN-225, and keep it flying, in thy mercy". And the Lord did bless it. And then St. Orville said: "First shalt thou lower the flaps. Then shalt thou advance the throttles to 3. Three shall be the number thou shalt advance the throttles to, and the number thou shalt advance the throttles to is 3. Thou shalt not advance them to 4, nor to 2, unless thou proceedeth to 3. FIVE IS RIGHT OUT!")

@BobJarvis zoom in on the image, I don't think they're faces. Not sure what they are though.  They look vaguely shell like, but only if a bit abstracted.  The bottom part has a vague resemblance to a B2 with the ragged back wing edge, in that case I'm not sure what the top bits are unless they're supposed to be a cloud of flairs.  OTOH a Soviet/Russian design is unlikely to use an image of a USAF aircraft in its styling.  An heavily abstracted bird perhaps?

You're right - they're not smiley faces. They appear to be...aliens from Space Invaders! (/face-smack/) How could I possibly have gotten that wrong?!?!? :-)

While only one was built, plus two copies which were built in Italy, the Dornier DO-X with twelve engines, is listed as having a flight crew of 10 to 14 during normal operation. Twelve of the relatively high maintenance engines of that era must have been a handful to keep operational during flights.
Dornier DO-X

While the Do-X certainly needed a big crew, I'm afraid the number of 14 includes stewards as well.

HP-1500 had 9 crew max but could have 8

Do you have any source for that?

Based on the armament listed in the Wikipedia article, it seems likely that the "eight or nine" includes three gunners and a bombardier.

authors: Bob Jarvis - Слава Україні


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How are Airbus pilots trained for using the mechanical backup control systems?
The A320 and friends have mechanical-only control capability (manual pitch trim + rudder pedals) for cases of total fly-by-wire computer or electrical failure.  Obviously, this would be covered in ground school when the various control laws are gone through.
However, is any further training given to line pilots on operating the aircraft this way? Or is it one of those "dusty corner" procedures that you learn about in ground school, but never really touch again?
Alternately, what would the chances be of someone who'd never flown a 'Bus in mechanical/backup law being able to keep the plane dirty-side-down and airborne long enough to get the FBW back going and/or perform a landing where the aircraft is reusable?  Clearly, it's non-nil as the Airbus test pilots actually tested flying the plane that way, but how difficult is the aircraft to fly in mechanical/backup law?

How much training do you think the airlines do?  Training costs money, and they are in it for profit.

@KorvinStarmast -- not training people also costs you big money...but I'm at the same time not sure how much training is needed to fly the 'Bus in mechanical backup law -- it could very well be that it's something your average line pilot could get the hang of the first time they had to try it "for real"

The amount of not training is addressed in insurance rates and risk assessments.  There are 12 threads, starting here here discussing the AF447 accident, and you will easily find five subsequent AB accidents on other threads nearby.  You might be interested to see what airline pilots think about the current state of training.

@KorvinStarmast: " Training costs money", image loss in the first accident costs much more.

@KorvinStarmast I assume they do as much training as is required by regulation (especially since the regulations are usually considered "sufficiently safe" by most airlines and insurance companies.)  If you read the full text of the question I think you'll note that one of the options is that it is not actually trained at all (second paragraph).  And perhaps that is the answer, but it would be good to hear from someone who trains on a A320 or is at least familiar with the rules surrounding what must be trained for.

You might consider adding a tag for EASA or FAA, I think the regulations will play into if this is trained for or not.  But that's going to vary by governing body.

@mins Emirates apparently doesn't worry about that, see recent 777 accident.

I'd be interested to see an answer form an A320 pilot who did the type rating course, and someone who flies on the line who gets sim sessions as part of the annual training (minimum) requirement.

In my particular case:

I probably did 10 minutes of demonstrating mechanical backup during initial type rating
I cannot remember for sure, but it never reappeared in any recurrent sim, and even if I did it was definitely not part of the syllabus, just something one of us pilots wanted to try.

There are several reasons for that:

Airbus definitely considers this to be a remote probability. I wonder if anyone ever had to use it for real in flight.
There is not much skill involved. You rotate a trim wheel until plane maintains altitude and you push on the rudder to keep (bring back?) wings level
The system is there to give minimum control for straight and level flight until the computers/electricity comes back online. It is not intended for the pilot to land (or even maneuver) using this

One important aspect that is often overlooked is that mechanical backup in an Airbus is, well, not mechanical in the sense that people think cables and pulleys. It is a mechanical connection to a hydraulic system that still needs pressure to operate. Losing 3 hyd you will lose mechanical trim.

According to AIRBUS but more specifically Airlines, have training syllabus.
Airbus Company states, clearly how, and how often to train Mechanical Backup Flying.
Each airline, which operates airbus A/Cs has to adhere with these recommendations and/or dictations.
Several failures of systems, or combination of failures can lead to the mechanical backup "state".
Every six months airline pilots are going to the Simulator for checking and training (LPC/OPC/SIM REC).

Of course there is training regarding mechanical backup.

How often?
It depends each time on the scenario, the seasonal systems to be trained, the systems failures, and many other factors.
Mechanical backup is a possible scenario by the Airbus, and well defined (but as always not exhaustive) in books, how can be happened. For this reason IMO all airliners provide this training to their pilots, and of course all the time (every six months) there is the possibility to fly a scenario leading to mechanical backup.

Generally the aircraft can fly and land with mechanical backup as long
  as the situation permits, the failures, the pilot skills, and plenty
  of other factors.

How difficult is?
1) Pilot Skills
2) Environment (Weather)
3) e.t.c (The list is non exhaustive at all.)

Aircraft manufacturers and airlines want to give proper and sufficient training to their pilots, and professional pilots want to
  receive proper and adequate training, and fly remote and difficult
  scenarios in the simulators, in order to be ready for "anything" that would be happened.
  So to summarise, and once again to answer your question, in general
  terms, YES airline pilots get training regularly, on the Mechanical Backup
  Scenario to FLY and to LAND the A/C  and the difficulty is
  something generic, for some people would be less difficult than some
  other.

I don't know where the quoted text comes from in this answer, or if it is just for formatting purposes, but there are some obviously wrong facts in there. Mechanical back-up in Airbus was never intended to land the a/c


text:
Do airline pilots identify failed engines in the same way as light aircraft pilots?
Do the two old adages of light multi-engine flying, namely "Dead foot, dead engine" and "Raise the dead", still apply when flying transport-category aircraft?  Or do airline pilots need to rely on their engine instruments in order to figure out which engine's kicked the bucket?
For those who aren't familiar with those memory aids, they are from page 12-21 (186 in PDF versions) of the FAA AFM:

There are two time-tested memory aids the pilot may find useful in dealing
  with engine-out scenarios. The first, “Dead foot–dead engine” is used to
  assist in identifying the failed engine. Depending on the failure mode, the
  pilot won’t be able to consistently identify the failed engine in a timely
  manner from the engine gauges. In maintaining directional control, however,
  rudder pressure will be exerted on the side (left or right) of the airplane
  with the operating engine. Thus, the “dead foot” is on the same side as the
  “dead engine.” Variations on this saying include “Idle foot–idle engine” and
  “Working foot–working engine.”
The second memory aid has to do with climb
  performance. The phrase “Raise the dead” is a reminder that the best climb
  performance is obtained with a very shallow bank, about 2° toward the
  operating engine. Therefore, the inoperative, or “dead” engine should be
  “raised” with a very slight bank.

You might want to explain those phrases for people who aren't familiar with them, it would help in understanding the question

Yes, the dead foot, dead engine does apply (but not as much as you might think), and, yes, airline pilots need to rely on their engine instruments in order to figure out which engine has failed, especially when you're flying a 4-engine aircraft. Actually, and with obvious prejudice, I prefer to say that the Flight Engineer will use the engine instruments to tell the Captain which engine has failed. Couldn't resist that.
Sudden loss of power on 727-100s and 747-100s/-200s is not nearly as noticeable as, say, on a Cessna 310. If you lose the middle engine (#2) on a 727, all you're going to notice is the loss of 1/3 of your power. Even the loss of engines 1 or 3 will not produce much yaw because they're mounted close to the aircraft centerline.
On the transport-category aircraft I flew it was unlikely that your foot would notice an in-flight engine failure because you took your feet off the rudder pedals as soon as you lifted off and didn't put them back on until short final. Adverse yaw was taken care of by the yaw damper.
If the loss of an engine came during descent at flight idle, the pilots might not notice it unless there is an obvious alert of some kind. We had one quit on us descending into Miami once and neither I nor the f.o. noticed it. Our alert was the f.e. saying something like, "We just lost #3." My increased work load consisted of simply saying something like, "See if you can get it running again. If it doesn't light off, forget it."
If you deliberately shut down an engine, you of course know which engine it is. That happened to me once. Again another vote for f.e.s. This one informed me that the oil pressure was dropping and oil temp climbing on one of the engines. He recommended shutting it down, which we did.
Generally speaking, when you lose an engine suddenly without warning when climbing out, I think the thing to remember is to take your time, fly the airplane with the configuration you have, and work the checklist for the situation at hand. That checklist will have procedures to ensure you shut down the engine that has failed, not one that's still operating. In other words, just do what you do in the sim every 6 months.

Agreed that losing the #2 on a three-holer won't be noticed by "dead foot, dead engine"...I was thinking more towards twins when I asked the question, but good answer anyway :)

@keelerjr12 And, as captain, you can turn off the no smoking sign! :-)

Of course these days you won't get F/E in most planes any more. But the avionics should give the warning instead.


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Do transatlantic flight plans have alternates routes?
Does every international flight have more than one flight route in the flight plan?
For example, after the incident with MH-17, most of the flights were diverted from that route. Were the alternate routes already planned or were they chosen at that moment? If they were chosen at that moment, who planned the new routes?

I believe that many flight plans include alternate airports, to be used in the event of emergency (not the same as an alternate flight plan). Someone who knows more than me might care to comment.

Each airborne flight has only one flightplan, which was submitted for that particular flight.
The routing is embedded into that flightplan and only that one routing is valid for that flight.
In case the routing is no longer available for the next flight due to airspace closure via NOTAM or airways being restricted by time of flight / day of flight, another routing will be used for that flight and submitted in the flightplan.
In case the routing needs to be changed for an already airborne flight, a new IFR clearance is read to the crew en-route, which alters the existing flightplan.
Alternate routings are usually managed by the airline's dispatch / planning centre and the best routing for a specific flight is created by the dispatchers, taking into account weather, NOTAMS, restrictions and many other factors.
En-route changes to a flightplan are made by ATC units and their data processing centres, if an impromptu change needs to be made due to airspace closures or other restrictions coming into effect which were unforseen.

Unless things have changed since I retired, a flight using the North Atlantic track system doesn't have its route across the North Atlantic embedded in the flight plan. The aircraft will be given the route in terms of lat/long just before entering the MNPS (Minimum Navigation Performance Specifications) airspace.

They are then cleared to the expected NAT entry fix and get the rest of the NAT when approaching the Oceanic boundary. I have however also seen aircraft with full routing across the NAT on clearance delivery. I'll try to get some citable sources. When did you retire @Terry?

My last flight was July 30, 1999, so I'm sure things have changed considerably.


text:
Can I have two speeds on one motor?
I am designing an aircraft and it is my first that will use a combustion engine rather than electric, so I am curious, if I had a single engine in the fuselage and gear shafts to the wings that drove propellers, how would I achieve different speeds on the propellers? The 'plane' itself is more similar to a VTOL so the different speeds are needed. I would be fine with a solution that used smaller electric motors in it's mechanism.
Or maybe I'm approaching this in a terribly inefficient way and there's a much better method to what I'm trying to achieve, I just feel stuck after battling it for a few days.
The aircraft itself will look similar to this:

Welcome to Aviation.SE. Unfortunately I do not see how your problem could fit in this site, my feeling is that you could be better off at Engineering

I think this question belongs more on http://electronics.stackexchange.com/

@Federico Should we try migrating this question?

@SMSvonderTann I do not know about migration (that's mod territory), but definitely I do not recommend electronics, Alexander wants to use a combustion engine, not an electrical one

@Federico Ah, I will just raise a flag for this to migrate then.

The thing you're looking for is a differential combined with a brake on each propeller, or a continuous variable transmission (CVT) for each propeller. Better still, just use two motors. :)

I don't think that electric versus combustion disqualifies this question, or the scale. [model-aircraft] is an existing tag. Now it may seem that the "different speed for propellers" makes if off-topic, but I believe that is an XY problem. I suspect the reason to ask that is stability&control, which is on topic.

Yes, a differential (wikipedia link) is the key .

It seems you also have a constraint to  not use variable pitch on the propeller blades, right?

You could add variable pitch to each prop to adjust the thrust each achieves? However, changing the pitch of either prop would change the load on the engine and therefore the speeds of both of them...

I'm not quite sure it is off-topic. Although this is about a model and the OP wants to use a differential, we may provide good hints nd pointer to solve the problem as if it where an helicopter model (e.g. variable pitch)

The short answer is you probably wouldn't do it this way: Designing a drive system which allows you to split the work force between two output shafts at an arbitrary ratio (effectively an active differential) is pretty complex, and failure-prone. The failure of the differential would be "problematic" (both rotors stop), and the failure of a single drive link would likely be catastrophic (one rotor stops in the VTOL configuration you have an extreme wing-over from the imbalanced thrust).
The generally preferred design for this type of aircraft has two full engines mounted on the wings (for example the V-22 Osprey).
Similar results can be achieved by vectoring thrust from a jet engine (as in the Harrier "Jump Jet"), which can be done with a single engine.

I figured this would be the case, thank you for the answer.

Although the Osprey has a pretty intricate system linking the rotors that allows either motor to drive both rotors should one motor fail.

@JörgWMittag Yup, that's to avoid the wing-over asymmetric thrust issue in case you lose an engine (which is a distinct possibility if, ya know, people are shooting at you). I think it also uses that linkage for starting them off the APU -- the Osprey is a pretty complicated beast to use as an example, but I couldn't think of another tilt-rotor V/STOL off the top of my head.

I don't think the fact that you failed to come up with an example of a non-complicated V/STOL tiltrotor is a problem with the top of your head ;-) Rather, I believe it is trying to tell us (and the OP) something about the inherent complexity of this particular niche in the aircraft design space.


text:
Does LSA hours count towards PPL training hours
I hold a LSA license wit 200 hours. I am currently doing my PPL and I was wondering if any of the SLA hours can count for some of my PPL training hours? What are the regulations?

Welcome to Aviation.SE! Could you please specify in which country you are in? the question is otherwise a tad too broad, as one would have to cover all the possible worldwide regulations.

I am not sure this is a complete duplicate, if it is about a different legislation, it is not.

If it's FAA then this is pretty much a dupe too


text:
Was the airframe involved in the LOT Flight 16 accident repaired?
The belly landing of LOT Flight 16 is known by many:

Wikimedia
YouTube

My impression is that a lot of aluminum was ground off by the runway. Maybe too much?
Question: What is the status of that aircraft today? Was it economically and safely repairable? Is it still flying?
And any general comments about the "repair or retire" decision after a costly breakdown or accident are welcome.
(I am impressed by the airmanship on that flight)

You asked about repairs: the famous Gimli glider suffered a nosewheel collapse on landing and scraped its nose. This was repairable and the aircraft re-entered normal service.